New forms of tuberculosis resistant to drugs used to treat the disease are proliferating around the world, especially in eastern Europe, experts warned yesterday.

Leading infectious disease experts at the World Health Organisation estimate that there are now 300,000 cases of multi drug-resistant TB worldwide. Almost 80% of these are resistant to at least three of the four main drugs used to treat the potentially lethal bacterial disease, according to a WHO report published yesterday.

While the biggest TB burden is in countries where public health systems are struggling, such as in the developing world and the former Soviet Union, in the days of frequent and easy international air travel, nobody is immune.

Paul Nunn, of the WHO's Stop TB department, said that aircraft passengers spread TB in a way that cannot be controlled. Unlike malaria when the interiors of planes leaving malarial zones are sprayed to kill mosquitos, tuberculosis is spread by passengers who may not know that they have it.

"The [Boeing] 747 is the vector of this disease and it is not susceptible to vector control," said Dr Nunn

Of particular concern is the strain called MDR TB. "We worry about MDR TB because untreated it is a death sentence," said Dr Nunn. "Treatment demands a cocktail of drugs which is expensive and difficult to administer."

The former Soviet Union is now "the MDR capital of the world," said Dr Nunn, with a rate almost 10 times that of anywhere else. But there are nearly 9m cases of TB around the world every year and 2m deaths.

There are around 40 to 50 cases of MDR TB in Britain every year - about 1% to 1.5% of TB cases - and the numbers appear to be fairly stable.

Paul Sommerfeld, founder of the charity TB Alert in the UK, said: "This is an airborne infectious disease. It is not possible to isolate any part of the world from the rest of the world."

There is TB screening at ports of entry, "but border controls have a very, very small role to play in this," he said. Better detection and treatment in the worst affected countries was needed.